Method of sizing paper with starch



Patented Dec. 21, 1943 NIETHOD F SIZING PAPER WITH STARCH Earle R. Edson, Gloucester, and Charles Quincy Ives, Reading, Mass, assignors to Le Pages Inc., Gloucester, Mass., a corporation of Massachusetts No Drawing. Application October 10,1940, Serial No. 360,594

9 Claims.

This invention relates to a method of sizing paper with starch and to starch compositions particularly adapted for the practice of such method. Its objective is to make possible starchsized paper products ofimproved physical characteristics, such as bursting-strength, tear-resistance, fold-endurance, etc.

In our application, Serial No. 261,666, filed March 13, 1939, issued into Patent No. 2,239,814 on April 29, 1941, we have disclosed for papersizing purpose a composition comprising a mixture of substantially dry rosin soap particles and substantially dry, acidic, calcined starch capable of swelling or gelatinizing quickly to yield highly viscous or gel-like aqueous solutions when mixed with about one to four times its weight in water at 70 F. We have further described in that application the value of adding such rosin-size starch composition to papermaking stock in the beater engine in the form of a relatively small unit weight within a sealed envelope or bag so as to promote the dispersion of such composition While submerged in water in the intensive zone of agitation and homogenization afforded by the bed plate and the beater roll of the engine, which defines between them an ingress or nip into which the sealed envelope or bag is immediately drawn upon being dropped into th beater engine. In other words, the sealed bags or units of the sizing composition, as they are drawn into the zone of intense beater-roll action, disintegrate with what might be termed explosive force so that suspension, dispersion, or solution of the sizing solids takes place very rapidly under water and under conditions of highsolids concentration to yield-a smooth suspension, dispersion, or solution of the sizing solids (i. e., a suspension or dispersion free from agglomeration or lumps), which, as further circulation of the stock about the engine is. effected, is homogene ously diluted throughout the stock. There is hence very little, if any, tendency for the sizing solids to stick to the walls or other parts of the beaterengine-as lumps or agglomerations or to fly away as dry dust into the atmosphere of the beater room and thus cause nuisance as 'well as constitute a loss.

We have now found that the foregoing prac-' tice as adding sizing composition to papermaking stock in the beater engine while enclosed or. confined within sealed paper envelopes or bags may be advantageously effected when'the composition is an all-starch composition and comprises more especially such substantially dry, acidic, calcined starch as has been disclosed in our aforementioned application, for such starch has precisely such property of quick swellability and dispersibility in water as comports with the desired smoothness and completeness of dispersion or suspension into and throughout the papermaking stock when such sealed envelopes or bags are exploded or burst under water in the zone or nip of intensive manipulation between the bed plate and beater roll, into which such envelopes or bags are drawn. Indeed, so quickly and smoothly dispersible are these acidic, calcined starches under these conditions that it even becomes possible to admix or compound therewith a relatively large proportion of raw or native starch and at the same time to realize in the finished paper products such improved physical characteristics as have heretofore been attained from relatively expensive, pre-solubilized or pregelatinized starches. When both an acidic, cal-' cined starch and raw starch constitute the sizing composition hereof, it is distinctly desirable to add to such composition a suitable activator or mixture of activators, such as urea and/or borax, which serve to activate the adhesive qualities of the raw starch, particularly while in the form of a concentrated solids suspension.

The acidic, calcined starch or starch-conversion product useful for the purpose hereof may be prepared by heat-treating or calcining an essentially' dry or solid raw starch under controlled conditions either in the absence or presence of a limited amount of water or acidic catalyzing agent, which agent in the form of an aqueous or liquid solution of appropriate strength may be applied, as by spraying, substantially uniformly to the raw starch for the purpose of moistening the latter for the heat treatment or calcination. While various acidic reagents may thus be applied to the raw starch, a distinctly preferable acidic catalyzing agent for preparing the acidic,

heat-treated or calcined starch useful for the purposes hereof consists essentially of an aqueous solution of hydrochloric acid, acetic acid, and formaldehyde. Such solution may be advantageously applied to the raw starch in amount to associate substantially uniformly with the starch intensive short-time, heat treatment is applied to the raw starch, say, a temperature of about 400 to 450 F. for a period of, say, only 5 to minutes, one should use the acidic reagents in amounts at the upper ends of the ranges hereinbefore indicated, whereas, when the heat treatment or calcination is conducted for a relatively long period of time, say, 1 to 16 hours, in developing a final temperature of say, 400 to 450 F., the amounts of acidic reagents should be at the lower ends of the ranges hereinbefore indicated in arriving at starch-conversion products of the swellability and dispersibility suitable for the purposes hereof. In any event, the resulting acidic, calcined, starch-conversion product is characterized by its rapid swellability and. dispersibility in water to yield highly viscou or gel-like aqueous solutions when mixed with about 1 to 4 times their weight of water at 70 F.; and such property of swellability and dispersibility has been found to go hand-in-hand with the development of the desired physical properties in paperproducts even when such starch-conversion product is compounded with a large proportion, say, even a preponderant proportion, of raw or native starch together with, say, one or more activators for the starch. In effect, the acidic, calcined starch serves as a carrier to enmesh or carry the raw or native starch granules in such manner that the raw or native starch granules 'are retained well by the papermaking stock in the course of the subsequent papermakving operations; and to this high retentivity by the papermaking stock of the raw starchgranules as well as the acidic, swollen, calcined starch granules are the improved physical characteristics of theresulting paper sheet attributable. The fact is that we have established retention values for the starch composition hereof comprising both acidicycalcined starch and raw or native starch practically as high as that ob-' tained When the sizing composition consisted of an all-acidic, calcined starch, despite the fact that the composition hereof may contain even more raw starch than the acidic, calcined starch component. In short, the carrying or enmeshing potency of the acidic, calcined starch used for the purposes hereof, is so great in admixture with papermaking stock that it can serve to'carry and fix on the papermaking stock, to practically as good advantage as an all-calcined starch, up

to approximately three times its own weight of various raw or native starches. It is thus possible by the compounding of calcined and raw starch in accordance with the present invention to secure important results in the beater-sizing of papermaking stock that cannot be realized by the use of either component alone. Thus, with raw starch alone, on the one hand, the

sizing eificiency or retention is relatively low,

(solids concentration in a conditioned in the beater engine. Specifically, 27 parts by weight of a substantially dry, acidic calcined starch, which has been prepared as hereinbefore described to acquire the desired quick swellability and dispersibility in water and which is available on the market, was admixed in a suitable dry mixer with 70 parts by weight of substantially dry, raw tapioca starch and a suitable amount of pulverulent starch activator, say, 2 parts by weight of urea and 1 part by weight of borax, until a substantially physically homogeneous composition was produced. Thereupon, the composition was weighed out as small fixed units of, say, 5 pounds, put into paper bags, and the bags sealed with a suitable adhesive.

Assuming, for example, that a beater engine is to be charged or furnished with a thousand pounds of papermaking stock on a dry basis and that it is desired to utilize about 3% of the starch composition hereof in the sizing of making stock so that the resulting stock has.

such substantial homogeneity or consistency as is desired for papermaking. Should rosin size and/or pigments and/or fillers be added to the papermaking stock along with the starch-sizing composition hereof, an amount of alum or equivalent fixative for such papermaking ingredients may be added, as usual, to'the stock. As already stated, the sealed bags or units of the starchsizing composition hereof are quickly drawn into the zone of the beater-roll action and are exploded or burst while submerged under the aqueous medium associated with the papermaking stock, wherefore, dispersion of the starch-sizing solids takes place rapidly at relatively very high zone of intense manipulation and homogenization. Accordingly, dispersion of the starch-sizing solids ensues quickly whereas, on the otherhand, the cost of an al'lcalcined starch. may be unduly high and, so far as concerns improved physical characteristics, conduce to no better results than in these instances of the present invention involving the use of the much less expensive compositions containing as much and even more raw starch than calcined starch (i. e. from a 1 to 1 ratio by weight to approximately a 3 to 1 ratio). I

We shall now detail a specific example of procedure in which a relatively large amount of raw or native starch was compounded with acidic, calcined starch and put up into sealed paper bags or other suitable containers for addition to papermaking stock as it is being beaten, or

is continued, the relatively concentrated, initially-generated dispersion is smoothly diluted or disseminated throughout the papermaking stock with the desired high retention of both the swollen calcined starch granules as well as the raw starch granules on the fibers. Th papermaking stock may otherwise be handled. as in ordinary papermaking practice to produce a finished, starch-sized paper product characterized by its improved physical characteristics.

The starch may be added as an enclosed unit package to the papermaking stock other than in a paper envelope or bag. Thus, a mass of pulverulent starch may be suitably capsulated, as within a jacket or skin of gelatine or other suitable binder compatible with the papermaking stock and readily dissolved or disintegrated by the aqueous vehicle of the papermaking stock to release or liberate the charge of pulverulent starch tinizing agents. In other instances, a, mass of pulverulent starch solids may be superficially encased with suitable binder media sprayed or otherwise applied thereunto in solution form, for

instance, a solution of glue or other collagenous material, gelatinized starch, sodium silicate, or equivalent binder, preferably of water-soluble or water-dispersible character. In short, the substantially dry pulverulent starch solids may be put into the form of brickettes or solid masses,

substantially only the exterior portions or layers of which are bound or fused together but which portions or layers are readily attacked and/or dissolved and/or dispersed by water to release or liberate the internal loose or pulverulent starch granules. In any event, it is thus seen that the beating operation is continued or sustained on the stock.

The "term starch is used herein in a comprehensive sense to include starches of various derivations, for instance, such root starches as tapioca and potato and such plant starches as corn, sago, etc. So far as concerns the term activator as used herein, it is meant to include the various adhesive activators or gelatinizing agents known to those skilled in the art, including various alkalies, such as sodium carbonate and caustic soda, and various organic compounds, such as the amides, the ureas, the thioureas, their analogues, homologues, etc. It is to be further understood that the illustrative example hereinbefore given is subject to considerable variation as regards the proportions of acidic, calcined starch and raw starch entering into the composition hereof. Generally speaking, the raw'starch may be present in the composition hereof in amount up to about three times the weight of the acidic, calcined starch component. Again, the amount of activator used in the composition hereof may be varied and, while for purpose of economy, it is generally desirable or necessary touse no more than about 2% of urea and 1% of. borax, based on the dry weight of the starch solids, yet it is possible to increase the amount of urea or other activator up to 5% or 10% or even greater, based on the weight of the starch, or to reduce the amount of such activator to a percentage lower than that indicated, say, to fractions of 1%. Generally speaking, the starch composition may be added to the papermaking stock in amounts ranging from about 1% to 5% starch solids, based on the dry weight of the papermaking stock, but, for some purposes, the amount of starch solids added may be as high as 10% or even greater, based on the dry weight of papermaking stock.

We claimf I 1. A method of making starch-sized paper involving the addition of starch to an aqueous suspension of papermaking stock in a beater engine, which comprises adding a starch composition inclusive of an acidic, calcined starch cornponent and up to about three times by weight of a raw starch component as an enclosed unit package to such stock as it is being beaten and stock to a beater engine together with suflicient' thereby causing such package to be swept into the zone of beater action, whereat said package is disintegrated to effect a dispersion of the starch solids below the surface of the stock; and continuing the beating operation on the stock to effect a substantially uniform dispersion ofv the starch solids throughout the stock.

2. A method of sizing paper, which comprises incorporating into the papermaking stock a starch-sizing composition consisting essentially of a dry pulverulent intimate mixture of .an acidic. calcined starch, raw starch, and a gelatinizing agent for the starch.

3. A method of sizing paper, which comprises I incorporating into the papermaking stock a starch-sizing composition consisting essentially of a dry pulverulent intimate mixture of an 7 acidic, calcined starch, raw starch, and a gelatinizing agent for the starch in the form of borax.

4. A method of sizing paper, which comprises incorporating into the papermaking stock a starch-sizing composition consisting essentially of a dry pulverulent intimate mixture of an acidic, calcined starch, rawstarch, and a gelatinizing agent for the starch in the form of urea.

5. A method of sizing paper, which comprises incorporating into the papermaking stock a starch-sizing composition comprising a dry pulverulent intimate mixture of an acidic, calcined starch component, a raw starch component in proportion of from approximately 1 to 1 to 3 to 1 by weight of the calcined, starch component, and a gelatinizing agent for the starch.

6. A method of making starch-sized paper involving the addition of starch to an aqueous suspension of papermaking stock in the beater engine, which comprises adding a starch-sizing composition inclusive of an acidic, calcined starch component and up to about three times by weight of a raw starch component together with a gelatinizing agent for the starch as an enclosed unit package to such stock as it is being beaten and thereby causing such package to be swept into the zoneof beater action, whereat said package is disintegrated to efiect a dispersion of the solids of said composition below the surface of the stock; and continuing the beating operation on the'stock to effect a substantially uniform dispersion of the solids of said composition throughout the stock.

7. In a method of making starch-sized paper involving the addition of starch-sizing t an aqueous suspension of papermaking stock in the beater engine, the steps which comprise adding the zone of beater action, whereat said package is disintegrated to effect a dispersion of the contents of said package below the surface of the stock, and continuing the beater operation on the stock to effect a substantially'uniform dispersion of the starch solids throughout the stock.

8. In a method of making starch-sized paper, the steps which comprise adding paper making water to enable circulation; also adding to the engine a substantially dry, pulverulent, papersizing composition inclusive of an acidic, starchconversion product while said composition is enclosed as a relatively small unit weight within a paper bag, and subjecting the resulting beater I contents to beating action, in the course of which v such bag is drawn into the zone of beater action whereat said bag is disintegrated to effect a dispersion of said pulverulent material under water throughout said stock, and continuing beating 5 said stock, composition and bag until a substantially physically homogeneous mixture of papermaking consistency is developed.

9. In a. method of making starch-sized paper requiring papermaking stock to be beaten in l0 water in a heater engine preparatory to papermaking, those steps which comprise adding such stock to said engine together with suflicient water to enable circulation of such stock; also adding to said engine a substantially dry, pulverulent paper-sizing composition inclusive of an acidic, calcined starch component while said 

